This is a thought experiment and I might be horribly wrong. If we have an electron-positron annihilation a photon pops into existence. This photon is then supposedly moving at speed of light at the exact moment that it pops into existence. How is this possible? Would the photon not have to accelerate to the speed of light? Of course this would mean it should experience time at the very brief moment it pops into existence. My mind is popping could someone help out?
$\begingroup$
$\endgroup$
1
-
$\begingroup$ Possible duplicates: physics.stackexchange.com/q/20289/2451 and links therein. $\endgroup$– Qmechanic ♦Commented Mar 21 at 18:37
Add a comment
|
1 Answer
$\begingroup$
$\endgroup$
6
Photons, which are elementary particles, don't accelerate similarly to normal objects. In the technical understanding acceleration is differentiated in terms of temporal change in velocity. On the other hand, photons necessarily have the speed of light in a vacuum under the fundamental laws of physics.
An interesting scenario in the realm of electron-positron annihilation is when an electron and a positron annihilate each other, they then become pure energy through the conversion of their mass. This energy can present itself in different forms of energy, although one of them would be the creation of photons. These photons do not come out being velocity zero before they are accelerated to the speed of light; they emerge as being formed already traveling at that speed.
Another example of this notion is shown in the Quantum Field Theory (QFT). The photon is an occurrence of electromagnetic field excitation. The electron and the positron, when annihilated, can mutually act through the electromagnetic field that drives the creation of photons. These photons are actually the oscillations or fluctuations of the electromagnetic field and they start to propagate at the speed of light once they are produced.
Indeed, in regarding the concept of time as a photon experience it is a bit complicated. Being massless particles, photons, in contrast to massive particles, ignore time by the theory of relativity. Considered from a photon's standpoint, which would undoubtedly exist if it were possible, as far as it is concerned, the trip from its creation to annihilation would be an instant one because no time dilation effects would have a place within the frame of the photon.
-
$\begingroup$ A photon really doesn't have a frame. See physics.stackexchange.com/q/724431/123208 & its network of linked questions $\endgroup$– PM 2RingCommented Mar 21 at 18:46
-
$\begingroup$ The electron moves through time; the photon does not. The photon is angular momentum that sits at the same 4D location, vibrating like a buzzer until something bumps into it and the bubble pops (the wave collapses). The null cone is an optical illusion due to our own motion through time. $\endgroup$ Commented Mar 22 at 2:14
-
$\begingroup$ @Miss_Understands The fact that the proper time for a photon is zero does not mean that it doesn’t move through an observer’s time (which is much more important than the photon’s proper time, because we observe it); it obviously does move through our time. Nor does it mean that the photon “sits at the same 4D location”; the solar photons we receive obviously move from the Sun to the Earth, and these are not the same 4D location. If comments could be downvoted, I would downvote yours as misinformation and non-mainstream physics. $\endgroup$– GhosterCommented Mar 22 at 6:56
-
$\begingroup$ @Miss_Understands Furthermore: the null cone is not an “optical illusion”; it is the foundation of the causal structure of spacetime. And it is not caused by our motion through time. $\endgroup$– GhosterCommented Mar 22 at 7:10
-
$\begingroup$ @ghost " we observe it); it obviously does move through our time." Thats the guy on a train looking out the window insisting a little too fervently that the telephone poles whizzing past must have legs. $\endgroup$ Commented Mar 22 at 12:05